How to bend a large model?
There are a few ways to bend a city like that.

One would be to create a curve that controls the deformation, and use it on a curve modifier applied to your city mesh.





The walls of the buildings will be perpendicular to the curve (and they might even crash into each other...)

Other very different option would be to use a lattice to control the deformation:

If you have the city and a curved plane.


Create a lattice that is olny one segment in height, line it up with the base of the city and dimension it to the with and depth of the city.



Select the city object, add a lattice deform modifier and choose the lattice you'd just created as the control object.



Select then the lattice, apply a shrinkwrap modifier and use the curved plane as target.



The lattice will deform to hug the plane, and the city will deform following the lattice. Note that in this case the top of the buildings will remain parallel to the curved plane but the walls will remain vertical on the Z axis and will not crash into each other this time. Maybe not quite what you're looking for, but another fun option to be aware of.